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pavank
Quartz | Level 8

Hi Everyone

Goodmornin

macro function %countdown having a numeric parameter and producing the following output in the log :

Countdown 10...

Countdown 9...

Countdown 8...

Countdown 7...

Countdown 6...

Countdown 5...

Countdown 4...

Countdown 3...

Countdown 2...

Countdown 1...

BOOM !!!

  1. Using a %do loop
  2. Using a recursive method

 

1 ACCEPTED SOLUTION

Accepted Solutions
Kurt_Bremser
Super User
%macro countdown(num);
%do i = &num. %to 1 %by -1;
  %put Countdown &i.;
%end;
%put Boom!;
%mend;

%countdown(10);

Study this closely, so you get a grasp on the very basics of macro programming.

Next, go searching for the concept of recursion in programming, and see how you can apply it to this task.

View solution in original post

17 REPLIES 17
pavank
Quartz | Level 8
data count;

var='countdown';
do i=n to 1 by -1;

put vari;
end;
stop;
run;

Could you please give solution

pavank
Quartz | Level 8

I didn't get any  idea how to do that 

pavank
Quartz | Level 8
%macro countdown(ds,num);
var='Countdown';
%do i= 10 %to  1 by -1;
output;
end;
stop;
put vari;
run;
%macro;

%countdown(ds,10);
%put(countdown.. &i);

I didn't get output ??

Kurt_Bremser
Super User
%macro countdown(num);
%do i = &num. %to 1 %by -1;
  %put Countdown &i.;
%end;
%put Boom!;
%mend;

%countdown(10);

Study this closely, so you get a grasp on the very basics of macro programming.

Next, go searching for the concept of recursion in programming, and see how you can apply it to this task.

pavank
Quartz | Level 8

THANK YOU VERY MUCH 

Tom
Super User Tom
Super User

There is no recursion in that example.

 

pavank
Quartz | Level 8
What is recursive method how to do recursive methof using bu above example
Tom
Super User Tom
Super User

Here is an introduction to the concept of recursion.

https://www.topcoder.com/thrive/articles/An%20Introduction%20to%20Recursion%20Part%20One

The SAS solution for your problems looks very much like the first example.

%macro countdown(start);
%if &start > 0 %then %do;
  %put Countdown &start;
  %countdown(%eval(&start-1))
%end;
%else %put BOOM !!!;
%mend countdown;
David_Billa
Rhodochrosite | Level 12
Why by -1 in do loop?
PaigeMiller
Diamond | Level 26

@David_Billa wrote:
Why by -1 in do loop?

If you want a loop to go from 10 to 9 to 8 to ..., what is the increment that gets you from 10 to 9?

--
Paige Miller

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